This invention relates in general to workpiece holding devices and in particular to a new and useful face driver for centering and driving workpieces to be chucked in a lathe.
The invention relates to a face driver for centering and driving workpieces chucked in a lathe, with a support which is connected to the lathe and supports a dead center and in which are inserted several driving pins which are uniformly distributed over the circumference and can be pressed against the workpiece to be chucked by means of a pressure plate acted upon centrally by a compression member.
A similar face driver is known from German OS No. 34 00 082. In this embodiment, the pressure plate is designed as a rigid component and clamped between a piston rod of an actuating piston disposed in a hydraulic cylinder and the driving pins. Since the piston rod end in contact with the pressure plate is convex and a return spring supported by the support and each driving pin is assigned to each driving pin, the pressure plate can assume an oblique position if the support is equipped with only two or three driving bolts so that the squareness errors of the workpiece must be compensated for accordingly, although this is not the purpose of this known face driver. In face drivers equipped with more than three driving pins, however, compensating squareness differences in the workpiece to be chucked is not possible in this manner.
Furthermore, no guidance and, hence, no defined position of the pressure plate is provided for, for which reason it can easily change its position during the return stroke of the actuating piston. Also, when chucking a workpiece, the force of the return springs must be overcome, which reduces the chucking force.